Backyard Aquaponics
A place to discuss aquaponics

My guess is you were looking in the regular plumbing section. Look in the Drain Waste Vent section and they'll probably have it http://www.homedepot.com/p/3-in-x-2-in-PVC-DWV-Reducing-Coupling-C4801HD32/100344038. Quite a few stores in the Phoenix area were listed as having this available.

You can have the timer run a few times a day as long as there is enough aeration when the pump isn't running. Same with not running it at night. Sometimes there is enough oxygen when the fish are young and small that you can do this at night without an air pump but you'll have to use good judgement on this one because it may not work.

Our nearest Home Depot is 80 miles away, so I get what I can from the local hardware stores. After all the plumbing I've done in 2015-2016 it seems I know what each store has or doesn't carry. I also recently learned what S&D pipe fittings are as @Scotty435 mentioned. When I had more money and because of the distance to Lowes and Home Depot I bought a lot of parts at Amazon. These days I use it more for reference. I get a picture on my phone and head into a hardware store and if I can't find what I'm looking for I can show them on my phone.

Scotty I'm with you on that picture, I never experimented with different pipe sizes, I built what was recommended here and it worked great. The only issue was getting that 90° elbow angled correctly to help stop the siphon effect.

Yea my project ran into budget problems, and I am a little scared with the powering of the pump as I have an nft system. For the nft system can there be a flood and drain system? Does there need to be a load of flow for the bell siphon to start?

The flow needs to be right for the siphon to kick in. I wouldn't worry about it though because if you set this up right you can ditch the siphon, run on a timer and put a hole in the standpipe so that the channels drain when the timer goes off. Anything below the hole remains in the channel for the plants between cycles. You might run into problems, you might not, I think it will work but I haven't done it this way so I'm not sure . I did run a tower system with orchids that were watered by sprayers intermittently - below these was a flood and drain tray with potted plants that functioned like the NFT channels without the siphon and everything did well.

I prefer the left one as well. Drains the growbeds quicker. More cycles per hour / more oxygen pushed through growbeds etc etc.

I prefer the left one too, but the photo shown is exaggerated compared to what I use. I use a 3/4 standpipe with a 2" bell. At the top I use a 3/4x1" flare.

I purchased said 3x2 inch reducer. It kind of does work, but now the siphon seems to not continue.

I'll add another +1 to the insistence that, if you use a timer, you don't need to mess with the siphon at all. You will be running a "timed flood and drain" with the top of the standpipe setting the flood level (high water overflow) and the hole drilled close to the bottom of the standpipe to handle the "drain" cycle when the pump shuts off.

I did have a backup with the hole drila led in. Now my hole is almost a cm wide.